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Re: XHTML 2.0 <datetime> element proposal

From: Christoph Päper <christoph.paeper@tu-clausthal.de>
Date: Sun, 2 Nov 2003 17:15:08 +0100
Message-ID: <00db01c3a15c$8e765a10$3ef4ae8b@heim4.tuclausthal.de>
To: <www-html@w3.org>
Cc: "Lachlan Hunt" <lhunt07@postoffice.csu.edu.au>

*Lachlan Hunt*:
>
> , there a 5 calenders in widespread use around the world --
> the Gregorian, Chinese, Hebrew, Persian and Islamic
>
>   Most of these calendars mentioned above have differ greatly in the
> length of one year, and thus the ISO format cannot represent any of
> these accurately because it is based on the Gregorian calendar only.

But there are algorithms to map the almost Gregorian date from ISO 8601 to all
those calendars. The easiest being ISO 8601 to Gregorian after the year 1582,
because it's 1:1.
Also AFAIK ISO/Gregorian date is recognized all over the world today, at least
better than the other calendars.

From the PDF of ISO 8601:2000(E) I have here (ISO/TC154N362):

| 1. Scope
| (...)
| This International Standard is applicable whenever dates and times are
| included in information interchange.
| This International Standard does not cover dates and times where words
| are used in the representation and dates and times where characters are
| not used in the representation. (...)
| This International Standard does not assign any particular meaning or
| interpretation to any data element that uses representations in accor-
| dance with this International Standard. Such meaning will be determined
| by the context of the application.

> How do you write the year 10BCE in ISO format?

  -0010

This cannot mean the tenth of the zeroest month, because there's nothing
between December and January and more important there would have to be two
dashes prefixed (5.2.1.3 d).
It cannot mean October of the year 00, which exists in ISO 8601 but not in the
Gregorian calendar, because negative years must have at least four digits
(5.1.2.4), but it could mean October of the double-zero year of the current
century (5.2.1.3 b, the first not the last of the 100 years).

To avoid ambiguities there should be "mutual agreement of the partners in
information interchange" for this cases, i.e. in our case the specification
has to specify it. So e.g., if we want to allow negative years, positive ones
should have a plus sign prefixed, if ambiguity is possible.

N.B.: If U+002D isn't used as delemiter *and* minus sign, there's no ambiguity
at all.

>   IMO, creating a system in XML that can represent all these calendars
> is *out of the scope of XHTML*,

Yes, absolutely.
Received on Sunday, 2 November 2003 11:16:19 UTC

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